Fluid heating furnace



Feb. 12, 1929. v 1,701,838 H. B. CANNON FLUID HEATING FURNACE Filed May 14, 1924 2 Sheets-Sheet 1 2 Sheets-Sheet 2 H B. CANNON FLUID HEATING FURNACE Filed May 14, 1924 II?! II- Feb. 12, 1929.

Patented Feb. 12, 1529. I

ESTATES 1,101,838 PATENT OFFICE.

HIRAM B. CANNON, OF METUCHEN, NEW JERSEY, ASSIGNOR TO THE CARBORUNQDUM COMPANY, OFNIAGARA. FALLS, 'NEW YORK, A CORPORATION OF PENNSYLVANIA.

FLUID HEATING FURNACE.

Application filed May 14, 1924. Serial No. 713,187.

This invention relates to apparatus or furnaces for burning pulverized fuel and, in the embodiment shown herein the apparatus is designed with special reference to the heating fluids contained in and circulating through tubes arranged in operative relation" to a-heat-radiating combustion chamber. It is the general purpose and object of the invention to provide a furnace or apparatus which will be capable of operating with pulverized fuel and which apparatus will be so constructed and arranged as to utilize a high percentage of the heat resulting from the combustion of the fuel; which will enable the heating to be accomplished with such fuel and with a. considerablereduction of furnace-volume or space over that usually required for equivalent heat capacity; also to provide an apparatus which will enable fluids contained in and circulating through tubes to be heated efiiciently by radiant heat as well as by such heat in conjunction with the exhaust gases.

In the drawings, Fig. 1 represents a vertical sectional view through a fluid heating apparatus embodying the invention; Fig. 2 a

transverse sectional view corresponding to the line 2-2 of Fig. 1; Fig. 3 a planview,

with parts broken away, of the combustion chamber shown inthe preceding views; and Fig. 4 an enlarged transverse sectional view 4 through the said combustion chamber;

The invention shown herein is embodied in a fluid heating furnace or apparatus of the type shown in co-pending application No. 713,186 filed May 14, 19224, which shows a furnace or apparatus of the same character as the one shown herein except that it is adapted for the burning of liquid fuel, such as oil. The invention as embodied herein is especially and primarily designed for the efficient burning of pulverized fuel, although certain features of construction (and particularly of the combustion chamber) are applicable-to and useful in connection with the combustion of other fuels. I

Describing the various parts by reference characters, 1 denotes the shell or envelope of a furnace, the said shell being formed of heatresistant material having low heat conductivity,'enabling it-to reflect heat without un; due absorption thereof. Material suitable for such shell is silocel mortar, magnesia covering, and similar material. The shell is closed at its front end by a head 2 having an opening 3 for the reception of a wind box 4;,

vided at its rear end with a neck 5. At its rear end, the shell 1 is provided with a stack 6, for exhaust gases. I

The shell 1 is shown as rectangular in cross section and is provided near the front and rear ends and nearthe middle thereof with inwardly-extending supporting and stabilizing frames or piers 7, the said frames or piers being seated within grooves 7 a formed in the top, bottom, and sides of the shell: Between the bottom of each frame or (pier and the bottom of the groove provided therefor there extends a supporting metal strap 8, the said strap extending upwardly in and through the side walls of the shell 1.

Projecting through the front of the wind box 4 is a burner nozzle 9, the said nozzle communicating with a T coupling 10 to which are connected "a supply 11, for pulverized fuel, and a pipe 12 supplying air under pressure for forming a primary mixture of air and fuel. Communicating with the bottom of the wind box is a pipe 13for supplying additional or secondary air to the wind box.

The nozzle 9 is arranged axially with respectito the neck 5 and preferably extends to approximately the rear-of such necli. This neck in turn-fits within a sleeve 14 formed with and projecting from the front of the combustion chamber. This combustion chamher is generally of the type shown in the patent to Hiram B. Gannon No. 1,371,774

issued March 15, 1921, and comprises va front wall 15 beyond which the sleeve 14 extends, a rear wall 16, a bottom wall 17, a top wa'll18, side wall 19, and a wall 20 intermediate between the side walls'and extending rearwardly from one side of the sleeve 14 to a point adjacent to but spaced from the rear wall 16 and forming a lateral mixing and combustion passage A and a lateral mixing tom wall slabs respectively. The top and bottom wall slabs are provided with seats 19 for 2 thereof, being supported upon the bottom fportionsof the frames or piers 6 and having its side walls closely adjacent to the side portions of said frames.

By the construction thus far shown and described, it will be apparent that the combustion chamber is supported above the bottom of the shell-1 and that it is spaced from the sides of such shell, a considerable space being left between the top of the chamber and the upper portions of the frames or piers 6. The space within the shell land surround- "ing the combustion chamber is utilized in a very efficient mannerfor the purpose of heating fluid. The fluidto be heated is conducted through coils of pipe surrounding the com- I ing extending l ngitudinally of the shell and 7 ber and jointly supported by the frames or bustion chamber and forming an absorbent screen. 21 denotes a'supply pipe leading to the coil, thecoilcomprising lengths 22 of tubconnected at thei nds by" bends 23, as is ordinary in heating apparatus. The tubes 22 are so arranged-as to provide anouter series of such tubes surrounding the combustion champiers. 7 and by the inner wall of the shell 1,

,with an inner series of such pipes also surcarbide or. carborundum. It will be noted is delivered to an outlet rounding the combustion chamber and mounted within the frames or piers 7, which frames or piers are also preferably of s licon further that the tubes in the inner series are staggered with respect to those in the outer series, thisarrangement permittingof a maximum absorption of radiant and reflected heat by the tubes. The fluid heated within the coil pipe 24leading to a suitable point of use.

It will be noted that the outlet D is located closely adjacent to the front wall 15, whereby the*products of combustion may pass upwardly and rearwardly in operative relation to the tubes 22 and be delivered'to the stack 6. The apparatus thus fa: disclosed may be suspended by the straps 8 from longitudinal I-beams 25 which are supported on the upper transverse members 26 of supporting frames; the vertical members .of which are indicated at 26. The upper ends of the'metal straps will be looped about themembers 2 5, as inv dicated at 8.

In order to accommodate the furnace or apparatus for the use of pulverized fuel, the

combustion-chamber should incline downwardly from front to rear, in order to prevent an undesirable accumulationof slag therewithin, the chamber being provided with an outlet E formed at the lower'end of the bot- 7 tom wall 17. Extending downwardly from and surrounding this outlet is a neclrF which communicates with an ash pit G normally sealed by a door G, the said pit being shown as formed within a large pier H upon whichthe rear end of the furnace shell is supported. The entire furnace, with the combustion chamber and the fluid heating tubes, is supported in the downwardly inclined position referred to hereinbefore, the rear and lower end ofthe furnace assembly being supported by the pier H.

In the operation of the apparatus thus far described, pulverized fuel will be delivered through the nozzle 9, neck 5, and sleeve 14, into the combustion passage A, and will burn therein and" in the passages C and B. For best results, the pulverized fuel and air will be so controlled that the flame will travel the full length of the combustion passages, with the tip of the flame at the outlet D. This insures combustion throughout the entire effective length of the combustion chamber, in-

cluding the three passages thereof. As a re sult, the chamber willbe uniformly heated throughout its extent, enabling it to operate at maximum'efliciency. The adjustment of the air and fuel to secure this result will be facilitated by providing the front wall 2 with a mica-covered peep hole located above the outlet D. The combustible mixture within and throughout the length of the passage B will be heated by the passage A'and the partition 20, facilitating the quick and complete combustion of the mixture in the passage B. i The tubes 22 will be heated by the radiant heat of, the combustion chamber as well as by the products of combustion delivered through the outlet D; but the length of the combustion chamber and the heat radiating qualities of the same are such that, by the time the flame has reached the outlet D, complete combustion of the mixture will have been obtained and the temperature of the products delivered througlfthe outlet D will have been so reduced that they may be discharged directly against the heatabsorbing tubes wlthout injury thereto. By employing material of high-heat-absorbing and radiat-- ing qualities for the frames or piers 6 the saidiframe or piers will be quickly heated and 150 i will transfer such heat to the tubes and to the fluid therewithin. Furthermore, the employment of a heat-resistant shell or envelope '1 of'low heat conductivity enables the said shell or envelope to reflect, without great ab sorption, heat radiated thereto by. the combustion chamber. The rays of heat directed "against thls envelope or casing will be reflected thereby to the tubes and absorbed by the latter.

Owing to the fact that the combustion chamber is made of slabs of silicon carbide, it will be advisable, if not necessary, to provide stabilizing members 25 beneath the joints between adjacent slabs, in addition to the frames or piers 6. These members may,

and preferably will, be made'of silicon car-' bide. j e

The particular structure shown herein will produce a fluid-heater of great efiiciency.

Where air, for instance, is heated, calorized tubes will preferably be used for the coil.

" Furthermore, by substituting headers for the bends 23 and by connecting the tubes 22 to such headers, the structure will produce a water tube boiler having great efliciency.

When operating at a high rate of combustion, a portion of the ash resulting from the combustion of the pulverized fuel is slagged and, becauseof the great heat radiation of the combustion chamber and heat absorption by the fluid tubes and envelope surrounding such chamber, this slag is cooled and deposited upon the inner walls and partition of the combustion chamber to a depth of approximately five-sixteenths inch. This slag coating is shown at 27 in Fig. 4; This coating or deposit does not build up any deeper or thicker because its presence tends to restrict the flow of heat to the furnace walls and, by

so doing, atempe ature is automatically built up which keeps the slagged ash molten beyond the depth mentioned.

' Due to the inclination 'of the furnace and combustion chamber, this molten ash or slag flows to the rear of the combustion chamber,

I where it-drops int-o'the ash pit G, whence it is drawn off periodically.

The use of silicon carbide for the combustion chamber prevents the latter from storing up heat to an extent which will bring its temperature as high as the fusing point of the ash in the pulverized fuel; so that, while the interior of the combustion chamber will be entirely covered with a protective ash glaze,

the temperature of the walls of the combustion chamber will never be'ashigh as the fusjury ,to or destruction of the latter.

ing point of the ash-in the pulverized fuel, and hence there will be .no reaction between the ash and the furnace walls, to cause in- On'the contrary, these walls will be-covered with a protective coating of ash glaze or slag which protects the walls from a wearing and abrasive action of the ash thereagainst. c

Should this protective coating crack, when thecombustion chamber cools ofi-after use, at

the joints between the slabs of which the said chamber is composed, at the next operation of the chamber, this coating will become molten to a sufficient extent to cause it to re-unite and close the cracks or j oints'thus formed because of the cooling operation.

Notwithstanding the fact that the production of ash is a necessary incident to the use of pulverized fuel when the combustion cham ber disclosed herein is operating under the most efiicient conditions, there will be no deposit of molten ash upon the tubes surrounding the said chamber. Such ash as may be discharged with the products of combustion through the outlet D, will be fine ash and will be discharged at a temperature insufficient to melt or fuse the same.

The construction disclosed herein realizes the general advantages of securing complete combustion of the fuel at very high 'combus tion capacity; transmitting nearly 60 per cent, by radiation, of the total heat resulting from the combustion in the fuel to the tubes or other absorbing media; heating the comheat-absorbing media.

In order to radiate heat efiiciently to the tubes or absorbent screen and to the interior of the casing 1, therefractory material of which the combustion chamber is composed should have a thermal conductivity in excess of 0.006 cal/cm /s ec/C.; and, as is well,

known, the thermal. conductivity of silicon carbide is in. excess of that expressed by this formula; Other refractories having a thermal conductivity in excess of that specified are fused aluminum oxide (A1 0,) and fused magnesium oxide (MgO) Having thus described my invention, what combustion chamber or to the surrounding I 1. A fiuid-heating apparatus comprising a combustion chamber composed principally of refractory material having a thermal conductivity in excess of 0.006 cal/cm /sec/C,

a plurality of tubes substantially surround ing the said combustion chamber and arranged in close proximity thereto and providing an absorbent screen for the radiant heat therefrom, the said combustion chamber and the said screen being inclined downwardly from the front to the rearthereof and the said combustion chamber being provided at the bottom of the rear portion thereof with an outlet for molten ash or slag, means for sealing said outlet, and means for supplying a' mixture of pulverized fueland'air to the front of said combustion chamber, the said combustion chamber havinga combustion space therein receiving at one end the mixture which all of the of pulverized fuel and air, and provided at its opposite end with outlet means through discharged.

2. A fluid-heating apparatus comprising an elongated combustion chamber composed principally of refractory material having a thermal conductivity in excess of 0.006

cal/cm /sec/G., a plurality of tubes extending longitudinally of .and substantially parallel with the said combustion chamber and substantially surrounding the said chamber in close proximity thereto and forming an absorbent screen for the radiant heat therefrom, the said combustion chamber and the said tubes being inclined downwardly from the front to the rear thereof and the said combustion chamber being provided at the hottom of the rear portion thereof with an out-' let for'molten ash or slag, and means for supplying a mixture of pulverized fuel and air to the front of said combustion chamber, the

- said combustion chamber having a combustion space therein receiving at oneend the mixture of pulverized fuel and 'air, and provided at its opposite end with outlet means through which all of the products of combustion are discharged 3. A fluid-heating apparatus comprising an elongated combustion chamber composed principally of refractory material having a thermal conductivity in excess of 0.006 cal/cm /sec/C., and a pluralityof tubes extending longitudinally of and substantially parallel with the top and sides of said'combustion chamber in close proximity thereto "and forming an absorbent screen for the radiant heat therefrom, the said combustion products of combustion are discharged.

chamber and the said tubes being inclined downwardly from the front to the rear thereof and the said combustion chamber being provided at the bot-tom of the rearportion' thereof with an outlet for molten ash or slag, and means for supplying a mixture of puls verized fuel and air toithe front of said combustion chamber, the said combust on chamher having a combustion space therein receiving at one end the mixture of pulverized fuel and air, and provided at its opposite end with outlet means through which all of the 4. A fluid-heatin apparatus comprising an outer casing ofheateresistant and heatreflecting material, a combustion chamber the'said combustion chamber being down wardly inclined from the front to the rear thereof and provided at the bottom of the rear portion thereof with an outlet for mol-v ten ash or slag leading to the atmosphere and products of combustion are meansfor sealing the same, and means for supplying a mixture of pulverized fuel and .air to the front of said combustion chamber, the combustion chamber, the tubes and the said casing being so arranged that theiubes will be heatedeffici-ently by radiation from the combustion chamber and by radiant heat received by theinterior of said casing and reflected thereby to said tubes.

5. .A fluid-heating apparatus comprising 'an outer casing of heat-resistant and heat-reflecting material, a combustion chamber composed principallyof refractory material havin a thermal conductivity in excess of 0.006 ca cm /s'ec/C. and mounted within the said casing, fluid-containing tubes arranged between the said chamber and the said casing,

the said combustion chamber being downwardly inclined from the front to the rear thereofand provided at the bottom of the rear portion thereof with an outlet for molten ash or slagleadingto the: atmosphere and means for sealing the same, and means for supplying a mixture of pulverized fuel and air to the front of said combustion chamber, the combustion chamber, the tubes and the said casing being so arranged that the tubes. will be heated efficiently by radiation from the combustionchamber and by radiant heat (received by the interior of said casing and reflected thereby to said tubes.

6. In a fluid-heating apparatus, the combination of an outer casing of heat-resistant and heat-reflecting material a combustion chamber, of refractory material having a thermal conductivity in excess of 0.006 cal/cm /sec/C. within said casing, fluidcontaining tubes arranged bet-weenthe said chamber and the said casing, the said tubes being staggered, thereby to produce an absorbent screen, the said combustion chamber being downwardly inclined from the front to the rear thereof and provided at the bottom of the rear portion thereof with an out let for molten ash pr slag leading to the at- 'mo'spliere and means for sealing the same,

and means for supplying a mixture of pulverized fuel and air to .the front of said combustion chamber, the combustion chamber, the tubes and the said casing being so ar-' ranged that the tubes will be heated efliciently by radiation from the combustion chamber and by radianbheat received by the interior of said casing and reflected thereby to said tubes.

7. A fluid-heating apparatus comprising an outer casin of heat-resistant and heat-re- 'flectirigmaterial, piers mounted within said casing and projecting inwardly from the inner wall thereof, a combustion chamber composed principally of refractory material hav- /cm"/sec/C. and extendinglongitudinalin a thermal conductivity in excess of 0.006

between the said chamber and said casing and mounted in the said piers, the said tubes being arranged in inner and outer series, the

tubes in one seriesbeing staggered with respect to those in another series, the casing, tubes and combustion chamber being downwardly inclined from the front to the rear thereof and the" chamber being provided at the,bottom of the rear portion thereof with an outlet for molten ash or slag leading to the atmosphere and means for sealing the same, and means'for supplying a mixture of pulverized fuel and. air to the front of said com bustion chamber, the combustion chamber,

the tubes and the said casing being so arranged that the tubes will be heated efliciently by radiation from the combustion'chamber with an outlet adjacent only-the said front wall at the opposite side of-said partition, the said combustion chamber being composed principally of refractory materialhaving athermal conductivity inexcess of 0.006 cal/cm /sec/G., and means for supplying mentioned opening. v

,such combustible mixture through the. first 9. A combustion chamber having front, 40.

back, top, bottom and side walls, with a vertical partition extending between the top and bottom walls and interposedbetween the side walls and extending from the front wall toward but spaced from the rear .wall to provide a passagewa therearound, the said combustion chamber eing. provided with an inlet for a combustible mixture in the front Wall at oneside of said partition and bein pro vided with an outlet in the top th-ereo adja cent to the front even only and on the opposide side of the partition, the said combustion chamberbeing composed principally of refractory material having a thermal conductivity in excess of 0.006 cal/cm /sec/G., and

means for supplying such combustible mixture through the first mentioned opening,

10. A fluid-heating apparatus comprismg an outer casing of heat-resistant and heat-refleeting material, a combustion chamber composed principally of silicon carbide mounted within the said casing, fluid-containing tubes arranged between the said chamber and the said casing, the said combustion chamber being downwardly inclined tfrom the front to the rear thereof and provided at the bottom of the rear portion thereof with an outlet for molten ash or slag leading to the atmosphere and means for sealing the same, and

means for supplying a mixture of pulverized 7 fuel and air to the front of said combustion chamber, the combustion chamber, the tubes andthe said casing being so arranged that the tubes will be heated efficiently byradiation from the combustion chamber and by radiant heat received 'byt-he interior of said casing and reflected thereby to said tubes.

In testimony whereof, I hereunto afix my signature. u

HIRAM B. cannon; 

